The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Why Am I Feeling Cold on Mounjaro?
Feeling cold while taking Mounjaro is a less commonly reported side effect, though some people do experience chills or sensitivity to temperature changes during treatment. Mounjaro (tirzepatide) works as a dual GIP and GLP-1 receptor agonist to support weight management, and changes in body composition and metabolic rate during weight loss can sometimes affect how your body regulates temperature. Understanding this side effect helps you manage it effectively and know when to speak with your GP.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
What Causes Feeling Cold on Mounjaro?
Feeling cold during Mounjaro treatment can happen for several reasons. As your body loses weight—particularly fat mass, which provides insulation—you may naturally feel colder in environments you previously found comfortable. Your metabolic rate (the speed at which your body burns calories) may also shift during weight loss, which can affect temperature regulation.
Additionally, Mounjaro can affect appetite and food intake significantly. If you're eating considerably less, your body has less fuel to generate heat through thermogenesis (the process of producing body warmth). Some people also report that Mounjaro-related nausea or reduced appetite may lead to nutritional gaps that can influence how well your body maintains its core temperature.
Chills are not listed as a very common side effect in clinical trials—they're less frequent than nausea, diarrhoea, or constipation—but individual responses vary. If you experience persistent chills alongside other symptoms like fever, contact your GP to rule out infection.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Managing Cold Sensitivity and When to Seek Help
Simple practical steps can help manage feeling cold: wear layered clothing you can adjust throughout the day, increase warm beverages like herbal tea, and ensure you're eating adequate nutrition to support your body's energy needs. Mounjaro dose titration (gradually increasing from 2.5 mg to your maintenance dose over weeks) may also play a role—some people find chills or temperature sensitivity settles as their body adapts.
Contact your GP if you experience sudden chills with fever, as this could indicate infection rather than a Mounjaro side effect. Also speak with them if feeling cold severely impacts your quality of life or if it worsens rather than improves after several weeks. Your GP can assess whether continuing your current Mounjaro UK prescription dose is right for you or if adjustments are needed. They can also rule out other causes like thyroid changes or vitamin deficiencies that sometimes accompany weight loss.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is feeling cold a common side effect of Mounjaro?
Feeling cold or chills is not listed as a very common side effect of Mounjaro in clinical trials. The most frequent side effects are nausea, diarrhoea, and constipation. However, individual responses vary, and changes in body composition and metabolic rate during weight loss can naturally affect temperature regulation in some people.
Can Mounjaro directly cause chills or fever?
Mounjaro itself doesn't typically cause fever, but persistent chills with fever could indicate infection. If you develop a fever alongside chills, contact your GP to rule out other causes. Mild chills related to reduced food intake or weight loss are more common than direct medication effects.
Should I stop taking Mounjaro if I feel cold all the time?
No—do not stop your Mounjaro without speaking to your GP first. Instead, contact your GP to discuss your symptoms. They can assess whether it's related to weight loss adaptation, nutritional factors, or something else, and help you decide whether to continue, adjust your dose, or explore other options.
How can I manage feeling cold while on Mounjaro?
Wear layered clothing, drink warm beverages, ensure adequate nutrition to support energy production, and stay active to generate body heat. These simple measures often help. Allow several weeks for your body to adapt as you progress through Mounjaro dose titration—symptoms often improve over time.
Could feeling cold on Mounjaro mean I'm losing weight too quickly?
gradual weight management can increase cold sensitivity, especially as your body loses insulating fat. The NHS recommends a safe loss of 0.5–1 kg per week. If you're losing faster than this or feeling unwell, speak with your GP about whether your current Mounjaro dose or calorie intake is appropriate for your health.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.